Which valve arrangement is least likely to cause refrigerant loss from a refrigeration system?

The best option, where the service valve is on the back seat, is the least likely to cause refrigerant loss from a refrigeration system. This configuration allows the refrigerant to be contained within the system more effectively when the valve is closed, as it prevents refrigerant from escaping into the atmosphere during servicing or maintenance.

When the service valve is seated at the back, it means that the refrigerant flow is focused through the valve seat that is furthest from the discharge line, which helps keep the refrigerant securely within the system. This placement minimizes the area of contact and the likelihood of leaks occurring at the valve.

In various contexts, having the service valve on the front seat presents a greater risk for refrigerant loss since it might allow refrigerant to escape more readily if not properly sealed or if the technicians are not careful when accessing or using the valve. Throttling and isolation valves may serve specific functions in the operation of the system, but they do not have the same effectiveness as a strategically placed back-seated valve in terms of preventing refrigerant loss.